Suchergebnisse

Full list of authors: Abdalla, H.; Abe, H.; Acero, F.; Acharyya, A.; Adam, R.; Agudo, I; Aguirre-Santaella, A.; Alfaro, R.; Alfaro, J.; Alispach, C.; Aloisio, R.; Batista, R. Alves; Amati, L.; Amato, E.; Ambrosi, G.; Anguner, E. O.; Araudo, A.; Armstrong, T.; Arqueros, F.; Arrabito, L.; Asano, K.; Ascasibar, Y.; Ashley, M.; Backes, M.; Balazs, C.; Balbo, M.; Balmaverde, B.; Baquero Larriva, A.; Martins, V. Barbosa; Barkov, M.; Baroncelli, L.; de Almeida, U. Barres; Barrio, J. A.; Batista, P-, I; Becerra Gonzalez, J.; Becherini, Y.; Beck, G.; Tjus, J. Becker; Belmont, R.; Benbow, W.; Bernardini, E.; Berti, A.; Berton, M.; Bertucci, B.; Beshley, V; Bi, B.; Biasuzzi, B.; Biland, A.; Bissaldi, E.; Biteau, J.; Blanch, O.; Bocchino, F.; Boisson, C.; Bolmont, J.; Bonanno, G.; Arbeletche, L. Bonneau; Bonnoli, G.; Bordas, P.; Bottacini, E.; Bottcher, M.; Bozhilov, V; Bregeon, J.; Brill, A.; Brown, A. M.; Bruno, P.; Bruno, A.; Bulgarelli, A.; Burton, M.; Buscemi, M.; Caccianiga, A.; Cameron, R.; Capasso, M.; Caprai, M.; Caproni, A.; Capuzzo-Dolcetta, R.; Caraveo, P.; Carosi, R.; Carosi, A.; Casanova, S.; Cascone, E.; Cauz, D.; Cerny, K.; Cerruti, M.; Chadwick, P.; Chaty, S.; Chen, A.; Chernyakova, M.; Chiaro, G.; Chiavassa, A.; Chytka, L.; Conforti, V; Conte, F.; Contreras, J. L.; Coronado-Blazquez, J.; Cortina, J.; Costa, A.; Costantini, H.; Covino, S.; Cristofari, P.; Cuevas, O.; D'Ammando, F.; Daniel, M. K.; Davies, J.; Dazzi, F.; De Angelis, A.; de Lavergne, M. de Bony; De Caprio, V; dos Anjos, R. de Cassia; Dal Pino, E. M. de Gouveia; De Lotto, B.; De Martino, D.; de Naurois, M.; Wilhelmi, E. de Ona; De Palma, F.; de Souza, V; Delgado, C.; Della Ceca, R.; della Volpe, D.; Depaoli, D.; Di Girolamo, T.; Di Pierro, F.; Diaz, C.; Diaz-Bahamondes, C.; Diebold, S.; Djannati-Atai, A.; Dmytriiev, A.; Dominguez, A.; Donini, A.; Dorner, D.; Doro, M.; Dournaux, J.; Dwarkadas, V. V.; Ebr, J.; Eckner, C.; Einecke, S.; Ekoume, T. R. N.; Elsaesser, D.; Emery, G.; Evoli, C.; Fairbairn, M.; Falceta-Goncalves, D.; Fegan, S.; Feng, Q.; Ferrand, G.; Fiandrini, E.; Fiasson, A.; Fioretti, V; Foffano, L.; Fonseca, M., V; Font, L.; Fontaine, G.; Franco, F. J.; Freixas Coromina, L.; Fukami, S.; Fukazawa, Y.; Fukui, Y.; Gaggero, D.; Galanti, G.; Gammaldi, V; Garcia, E.; Garczarczyk, M.; Gascon, D.; Gaug, M.; Gent, A.; Ghalumyan, A.; Ghirlanda, G.; Gianotti, F.; Giarrusso, M.; Giavitto, G.; Giglietto, N.; Giordano, F.; Glicenstein, J.; Goldoni, P.; Gonzalez, J. M.; Gourgouliatos, K.; Grabarczyk, T.; Grandi, P.; Granot, J.; Grasso, D.; Green, J.; Grube, J.; Gueta, O.; Gunji, S.; Halim, A.; Harvey, M.; Collado, T. Hassan; Hayashi, K.; Heller, M.; Cadena, S. Hernandez; Hervet, O.; Hinton, J.; Hiroshima, N.; Hnatyk, B.; Hnatyk, R.; Hoffmann, D.; Hofmann, W.; Holder, J.; Horan, D.; Horandel, J.; Horvath, P.; Hovatta, T.; Hrabovsky, M.; Hrupec, D.; Hughes, G.; Hutten, M.; Iarlori, M.; Inada, T.; Inoue, S.; Insolia, A.; Ionica, M.; Iori, M.; Jacquemont, M.; Jamrozy, M.; Janecek, P.; Jimenez Martinez, I; Jin, W.; Jung-Richardt, I; Jurysek, J.; Kaaret, P.; Karas, V; Karkar, S.; Kawanaka, N.; Kerszberg, D.; Khelifi, B.; Kissmann, R.; Knodlseder, J.; Kobayashi, Y.; Kohri, K.; Komin, N.; Kong, A.; Kosack, K.; Kubo, H.; La Palombara, N.; Lamanna, G.; Lang, R. G.; Lapington, J.; Laporte, P.; Lefaucheur, J.; Lemoine-Goumard, M.; Lenain, J.; Leone, F.; Leto, G.; Leuschner, F.; Lindfors, E.; Lloyd, S.; Lohse, T.; Lombardi, S.; Longo, F.; Lopez, A.; Lopez, M.; Lopez-Coto, R.; Loporchio, S.; Lucarelli, F.; Luque-Escamilla, P. L.; Lyard, E.; Maggio, C.; Majczyna, A.; Makariev, M.; Mallamaci, M.; Mandat, D.; Maneva, G.; Manganaro, M.; Manico, G.; Marcowith, A.; Marculewicz, M.; Markoff, S.; Marquez, P.; Marti, J.; Martinez, O.; Martinez, M.; Martinez, G.; Martinez-Huerta, H.; Maurin, G.; Mazin, D.; Mbarubucyeye, J. D.; Miranda, D. Medina; Meyer, M.; Micanovic, S.; Miener, T.; Minev, M.; Miranda, J. M.; Mitchell, A.; Mizuno, T.; Mode, B.; Moderski, R.; Mohrmann, L.; Molina, E.; Montaruli, T.; Moralejo, A.; Morales Merino, J.; Morcuende-Parrilla, D.; Morselli, A.; Mukherjee, R.; Mundell, C.; Murach, T.; Muraishi, H.; Nagai, A.; Nakamori, T.; Nemmen, R.; Niemiec, J.; Nieto, D.; Nievas, M.; Nikolajuk, M.; Nishijima, K.; Noda, K.; Nosek, D.; Nozaki, S.; Ohira, Y.; Ohishi, M.; Oka, T.; Ong, R. A.; Orienti, M.; Orito, R.; Orlandini, M.; Orlando, E.; Osborne, J. P.; Ostrowski, M.; Oya, I; Pagliaro, A.; Palatka, M.; Paneque, D.; Pantaleo, F. R.; Paredes, J. M.; Parmiggiani, N.; Patricelli, B.; Pavletic, L.; Pe'er, A.; Pech, M.; Pecimotika, M.; Peresano, M.; Persic, M.; Petruk, O.; Pfrang, K.; Piatteli, P.; Pietropaolo, E.; Pillera, R.; Pilszyk, B.; Pimentel, D.; Pintore, F.; Pita, S.; Pohl, M.; Poireau, V; Polo, M.; Prado, R. R.; Prast, J.; Principe, G.; Produit, N.; Prokoph, H.; Prouza, M.; Przybilski, H.; Pueschel, E.; Puehlhofer, G.; Pumo, M. L.; Punch, M.; Queiroz, F.; Quirrenbach, A.; Rando, R.; Razzaque, S.; Rebert, E.; Recchia, S.; Reichherzer, P.; Reimer, O.; Reimer, A.; Renier, Y.; Reposeur, T.; Rhode, W.; Ribeiro, D.; Ribo, M.; Richtler, T.; Rico, J.; Rieger, F.; Rizi, V; Rodriguez, J.; Fernandez, G. Rodriguez; Ramirez, J. C. Rodriguez; Rodriguez Vazquez, J. J.; Romano, P.; Romeo, G.; Roncadelli, M.; Rosado, J.; de Leon, A. Rosales; Rowell, G.; Rudak, B.; Rujopakarn, W.; Russo, F.; Sadeh, I; Saha, L.; Saito, T.; Greus, F. Salesa; Sanchez, D.; Sanchez-Conde, M.; Sangiorgi, P.; Sano, H.; Santander, M.; Santos, E. M.; Sanuy, A.; Sarkar, S.; Saturni, F. G.; Sawangwit, U.; Scherer, A.; Schleicher, B.; Schovanek, P.; Schussler, F.; Schwanke, U.; Sciacca, E.; Scuderi, S.; Arroyo, M. Seglar; Sergijenko, O.; Servillat, M.; Seweryn, K.; Shalchi, A.; Sharma, P.; Shellard, R. C.; Siejkowski, H.; Sinha, A.; Sliusar, V; Slowikowska, A.; Sokolenko, A.; Sol, H.; Specovius, A.; Spencer, S.; Spiga, D.; Stamerra, A.; Starling, R.; Stolarczyk, T.; Straumann, U.; Striskovic, J.; Suda, Y.; Tagliaferri, G.; Takahashi, H.; Takahashi, M.; Tavecchio, F.; Taylor, L.; Tejedor, L. A.; Temnikov, P.; Terrier, R.; Terzic, T.; Testa, V; Tian, W.; Tibaldo, L.; Tonev, D.; Torres, D. F.; Torresi, E.; Tosti, L.; Tothill, N.; Tovmassian, G.; Travnicek, P.; Truzzi, S.; Tuossenel, F.; Umana, G.; Vacula, M.; Vagelli, V.; Valentino, M.; Vallage, B.; Vallania, P.; van Eldik, C.; Varner, G. S.; Vassiliev, V.; Vazquez Acosta, M.; Vecchi, M.; Veh, J.; Vercellone, S.; Vergani, S.; Verguilov, V.; Vettolani, G. P.; Viana, A.; Vigorito, C. F.; Vitale, V.; Vorobiov, S.; Vovk, I; Vuillaume, T.; Wagner, S. J.; Walter, R.; Watson, J.; White, M.; White, R.; Wiemann, R.; Wierzcholska, A.; Will, M.; Williams, D. A.; Wischnewski, R.; Wolter, A.; Yamazaki, R.; Yanagita, S.; Yang, L.; Yoshikoshi, T.; Zacharias, M.; Zaharijas, G.; Zaric, D.; Zavrtanik, M.; Zavrtanik, D.; Zdziarski, A. A.; Zech, A.; Zechlin, H.; Zhdanov, V., I; Zivec, M. ; The Cherenkov Telescope Array (CTA), the new-generation ground-based observatory for γ astronomy, provides unique capabilities to address significant open questions in astrophysics, cosmology, and fundamental physics. We study some of the salient areas of γ cosmology that can be explored as part of the Key Science Projects of CTA, through simulated observations of active galactic nuclei (AGN) and of their relativistic jets. Observations of AGN with CTA will enable a measurement of γ absorption on the extragalactic background light with a statistical uncertainty below 15% up to a redshift z=2 and to constrain or detect γ halos up to intergalactic-magnetic-field strengths of at least 0.3 pG . Extragalactic observations with CTA also show promising potential to probe physics beyond the Standard Model. The best limits on Lorentz invariance violation from γ astronomy will be improved by a factor of at least two to three. CTA will also probe the parameter space in which axion-like particles could constitute a significant fraction, if not all, of dark matter. We conclude on the synergies between CTA and other upcoming facilities that will foster the growth of γ cosmology. © 2021 IOP Publishing Ltd and Sissa Medialab. ; We gratefully acknowledge financial support from the following agencies and organizations: State Committee of Science of Armenia, Armenia; The Australian Research Council, Astronomy Australia Ltd, The University of Adelaide, Australian National University, Monash University, The University of New South Wales, The University of Sydney, Western Sydney University, Australia; Federal Ministry of Education, Science and Research, and Innsbruck University, Austria; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ), Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Ministry of Science, Technology, Innovations and Communications (MCTIC), Brasil; Ministry of Education and Science, National RI Roadmap Project DO1-153/28.08.2018, Bulgaria; The Natural Sciences and Engineering Research Council of Canada and the Canadian Space Agency, Canada; CONICYT-Chile grants CATA AFB 170002, ANID PIA/APOYO AFB 180002, ACT 1406, FONDECYT-Chile grants, 1161463, 1170171, 1190886, 1171421, 1170345, 1201582, Gemini-ANID 32180007, Chile; Croatian Science Foundation, Rudjer Boskovic Institute, University of Osijek, University of Rijeka, University of Split, Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, University of Zagreb, Faculty of Electrical Engineering and Computing, Croa tia; Ministry of Education, Youth and Sports, MEYS M2015046, LM2018105, LTT17006, EU/MEYS CZ.02.1.01/0.0/0.0/16_013/0001403, CZ.02.1.01/0.0/0.0/18_046/0016007 and CZ.02.1.01/0.0/0.0/16_019/0000754, Czech Republic; Academy of Finland (grant nr.317636 and 320045), Finland; Ministry of Higher Education and Research, CNRS-INSU and CNRS-IN2P3, CEA-Irfu, ANR, Regional Council Ile de France, Labex ENIGMASS, OCEVU, OSUG2020 and P2IO, France; Max Planck Society, BMBF, DESY, Helmholtz Association, Germany; Department of Atomic Energy, Department of Science and Technology, India; Istituto Nazionale di Astrofisica (INAF), Istituto Nazionale di Fisica Nucleare (INFN), MIUR, Istituto Nazionale di Astrofisica (INAF-OABRERA) Grant Fondazione Cariplo/Regione Lombardia ID 2014-1980/RST_ERC, Italy; ICRR, University of Tokyo, JSPS, MEXT, Japan; Netherlands Research School for Astronomy (NOVA), Netherlands Organization for Scientific Research (NWO), Netherlands; University of Oslo, Norway; Ministry of Science and Higher Education, DIR/WK/2017/12, the National Centre for Research and Development and the National Science Centre, UMO-2016/22/M/ST9/00583, Poland; Slovenian Research Agency, grants P1-0031, P1-0385, I0-0033, J1-9146, J1-1700, N1-0111, and the Young Researcher program, Slovenia; South African Department of Science and Technology and National Research Foundation through the South African Gamma-Ray Astronomy Programme, South Africa; The Spanish groups acknowledge the Spanish Ministry of Science and Innovation and the Spanish Research State Agency (AEI) through grants AYA2016-79724-C4-1-P, AYA2016-80889-P, AYA2016-76012-C3-1-P, BES-2016-076342, FPA2017-82729-C6-1-R, FPA2017-82729-C6-2-R, FPA2017-82729-C6-3-R, FPA2017-82729-C6-4-R, FPA2017-82729-C6-5-R, FPA2017-82729-C6-6-R, PGC2018-095161-B-I00, PGC2018-095512-B-I00, PID2019-107988GB-C22; the "Centro de Excelencia Severo Ochoa" program through grants no. SEV-2016-0597, SEV-2016-0588, SEV-2017-0709, CEX2019-000920-S; the "Unidad de Excelencia María de Maeztu" program through grant no. MDM-2015-0509; the "Ramón y Cajal" programme through grants RYC-2013-14511, RYC-2017-22665; and the MultiDark Consolider Network FPA2017-90566-REDC. They also acknowledge the Atracción de Talento contract no. 2016-T1/TIC-1542 granted by the Comunidad de Madrid; the "Postdoctoral Junior Leader Fellowship" programme from La Caixa Bank ing Foundation, grants no. LCF/BQ/LI18/11630014 and LCF/BQ/PI18/11630012; the "Programa Operativo" FEDER 2014-2020, Consejería de Economía y Conocimiento de la Junta de Andalucía (Ref. 1257737), PAIDI 2020 (Ref. P18-FR-1580) and Universidad de Jaén; "Programa Operativo de Crecimiento Inteligente" FEDER 2014-2020 (Ref. ESFRI-2017-IAC-12), Ministerio de Ciencia e Innovación, 15% co-financed by Consejería de Economía, Industria, Comercio y Conocimiento del Gobierno de Canarias; the Spanish AEI EQC2018-005094-P FEDER 2014-2020; the European Union's "Horizon 2020" research and innovation programme under Marie Skłodowska-Curie grant agreement no. 665919; and the ESCAPE project with grant no. GA:824064; Swedish Research Council, Royal Physiographic Society of Lund, Royal Swedish Academy of Sciences, The Swedish National Infrastructure for Computing (SNIC) at Lunarc (Lund), Sweden; State Secretariat for Education, Research and Innovation (SERI) and Swiss National Science Foundation (SNSF), Switzerland; Durham University, Leverhulme Trust, Liverpool University, University of Leicester, University of Oxford, Royal Soci ety, Science and Technology Facilities Council, UK; U.S. National Science Foundation, U.S. Department of Energy, Argonne National Laboratory, Barnard College, University of California, University of Chicago, Columbia University, Georgia Institute of Technology, Institute for Nuclear and Particle Astrophysics (INPAC-MRPI program), Iowa State University, the Smithsonian Institution, Washington University McDonnell Center for the Space Sciences, The University of Wisconsin and the Wisconsin Alumni Research Foundation, USA. The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreements No 262053 and No 317446. This project is receiving funding from the European Union's Horizon 2020 research and innovation programs under agreement No 676134. The research leading to these results has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement GammaRayCascades No 843800. The Fermi LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States, the Commissariat à l'Energie Atomique and the Centre National de la Recherche Scientifique / Institut National de Physique Nucléaire et de Physique des Particules in France, the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK) and Japan Aerospace Exploration Agency (JAXA) in Japan, and the K. A. Wallenberg Foundation, the Swedish Research Council and the Swedish National Space Board in Sweden. Additional support for science analysis during the operations phase is gratefully acknowledged from the Istituto Nazionale di Astrofisica in Italy and the Centre National d'Études Spatiales in France. This work performed in part under DOE Contract DE-AC02-76SF00515. ; Peer reviewed

Full list of authors: Acciari, V. A.; Ansoldi, S.; Antonelli, L. A.; Arbet Engels, A.; Artero, M.; Asano, K.; Babić, A.; Baquero, A.; Barres de Almeida, U.; Barrio, J. A.; Batković, I.; Becerra González, J.; Bednarek, W.; Bellizzi, L.; Bernardini, E.; Bernardos, M.; Berti, A.; Besenrieder, J.; Bhattacharyya, W.; Bigongiari, C.; Blanch, O.; Bošnjak, Ž.; Busetto, G.; Carosi, R.; Ceribella, G.; Cerruti, M.; Chai, Y.; Chilingarian, A.; Cikota, S.; Colak, S. M.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; D'Amico, G.; D'Elia, V.; da Vela, P.; Dazzi, F.; de Angelis, A.; de Lotto, B.; Delfino, M.; Delgado, J.; Delgado Mendez, C.; Depaoli, D.; di Pierro, F.; di Venere, L.; Do Souto Espiñeira, E.; Dominis Prester, D.; Donini, A.; Doro, M.; Fallah Ramazani, V.; Fattorini, A.; Ferrara, G.; Fonseca, M. V.; Font, L.; Fruck, C.; Fukami, S.; García López, R. J.; Garczarczyk, M.; Gasparyan, S.; Gaug, M.; Giglietto, N.; Giordano, F.; Gliwny, P.; Godinović, N.; Green, J. G.; Green, D.; Hadasch, D.; Hahn, A.; Heckmann, L.; Herrera, J.; Hoang, J.; Hrupec, D.; Hütten, M.; Inada, T.; Inoue, S.; Ishio, K.; Iwamura, Y.; Jiménez, I.; Jormanainen, J.; Jouvin, L.; Kajiwara, Y.; Karjalainen, M.; Kerszberg, D.; Kobayashi, Y.; Kubo, H.; Kushida, J.; Lamastra, A.; Lelas, D.; Leone, F.; Lindfors, E.; Lombardi, S.; Longo, F.; López-Coto, R.; López-Moya, M.; López-Oramas, A.; Loporchio, S.; Machado de Oliveira Fraga, B.; Maggio, C.; Majumdar, P.; Makariev, M.; Mallamaci, M.; Maneva, G.; Manganaro, M.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Menchiari, S.; Mender, S.; Mićanović, S.; Miceli, D.; Miener, T.; Minev, M.; Miranda, J. M.; Mirzoyan, R.; Molina, E.; Moralejo, A.; Morcuende, D.; Moreno, V.; Moretti, E.; Neustroev, V.; Nigro, C.; Nilsson, K.; Nishijima, K.; Noda, K.; Nozaki, S.; Ohtani, Y.; Oka, T.; Otero-Santos, J.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Pavletić, L.; Peñil, P.; Perennes, C.; Persic, M.; Prada Moroni, P. G.; Prandini, E.; Priyadarshi, C.; Puljak, I.; Ribó, M.; Rico, J.; Righi, C.; Rugliancich, A.; Saha, L.; Sahakyan, N.; Saito, T.; Sakurai, S.; Satalecka, K.; Saturni, F. G.; Schmidt, K.; Schweizer, T.; Sitarek, J.; Šnidarić, I.; Sobczynska, D.; Spolon, A.; Stamerra, A.; Strom, D.; Strzys, M.; Suda, Y.; Surić, T.; Takahashi, M.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Teshima, M.; Tosti, L.; Truzzi, S.; Tutone, A.; Ubach, S.; van Scherpenberg, J.; Vanzo, G.; Vazquez Acosta, M.; Ventura, S.; Verguilov, V.; Vigorito, C. F.; Vitale, V.; Vovk, I.; Will, M.; Wunderlich, C.; Zarić, D.; Baack, D.; Balbo, M.; Biederbeck, N.; Biland, A.; Bretz, T.; Buss, J.; Dorner, D.; Eisenberger, L.; Elsaesser, D.; Hildebrand, D.; Iotov, R.; Mannheim, K.; Neise, D.; Noethe, M.; Paravac, A.; Rhode, W.; Schleicher, B.; Sliusar, V.; Walter, R.; D'Ammando, F.; Horan, D.; Lien, A. Y.; Baloković, M.; Madejski, G. M.; Perri, M.; Verrecchia, F.; Leto, C.; Lähteenmäki, A.; Tornikoski, M.; Ramakrishnan, V.; Järvelä, E.; Vera, R. J. C.; Chamani, W.; Villata, M.; Raiteri, C. M.; Gupta, A. C.; Pandey, A.; Fuentes, A.; Agudo, I.; Casadio, C.; Semkov, E.; Ibryamov, S.; Marchini, A.; Bachev, R.; Strigachev, A.; Ovcharov, E.; Bozhilov, V.; Valcheva, A.; Zaharieva, E.; Damljanovic, G.; Vince, O.; Larionov, V. M.; Borman, G. A.; Grishina, T. S.; Hagen-Thorn, V. A.; Kopatskaya, E. N.; Larionova, E. G.; Larionova, L. V.; Morozova, D. A.; Nikiforova, A. A.; Savchenko, S. S.; Troitskiy, I. S.; Troitskaya, Y. V.; Vasilyev, A. A.; Merkulova, O. A.; Chen, W. P; Samal, M.; Lin, H. C.; Moody, J. W.; Sadun, A. C.; Jorstad, S. G.; Marscher, A. P.; Weaver, Z. R.; Feige, M.; Kania, J.; Kopp, M.; Kunkel, L.; Reinhart, D.; Scherbantin, A.; Schneider, L.; Lorey, C.; Acosta-Pulido, J. A.; Carnerero, M. I.; Carosati, D.; Kurtanidze, S. O.; Kurtanidze, O. M.; Nikolashvili, M. G.; Chigladze, R. A.; Ivanidze, R. Z.; Kimeridze, G. N.; Sigua, L. A.; Joner, M. D.; Spencer, M.; Giroletti, M.; Marchili, N.; Righini, S.; Rizzi, N.; Bonnoli, G.; MAGIC Collaboration; Fact Collaboration.-- This is an Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ; Aims. We present a detailed characterisation and theoretical interpretation of the broadband emission of the paradigmatic TeV blazar Mrk 421, with a special focus on the multi-band flux correlations. Methods. The dataset has been collected through an extensive multi-wavelength campaign organised between 2016 December and 2017 June. The instruments involved are MAGIC, FACT, Fermi-LAT, Swift, GASP-WEBT, OVRO, Medicina, and Metsahovi. Additionally, four deep exposures (several hours long) with simultaneous MAGIC and NuSTAR observations allowed a precise measurement of the falling segments of the two spectral components. Results. The very-high-energy (VHE; E 100 GeV) gamma rays and X-rays are positively correlated at zero time lag, but the strength and characteristics of the correlation change substantially across the various energy bands probed. The VHE versus X-ray fluxes follow dierent patterns, partly due to substantial changes in the Compton dominance for a few days without a simultaneous increase in the X-ray flux (i.e., orphan gamma-ray activity). Studying the broadband spectral energy distribution (SED) during the days including NuSTAR observations, we show that these changes can be explained within a one-zone leptonic model with a blob that increases its size over time. The peak frequency of the synchrotron bump varies by two orders of magnitude throughout the campaign. Our multi-band correlation study also hints at an anti-correlation between UV-optical and X-ray at a significance higher than 3. A VHE flare observed on MJD 57788 (2017 February 4) shows gamma-ray variability on multi-hour timescales, with a factor ten increase in the TeV flux but only a moderate increase in the keV flux. The related broadband SED is better described by a two-zone leptonic scenario rather than by a one-zone scenario.We find that the flare can be produced by the appearance of a compact second blob populated by high energetic electrons spanning a narrow range of Lorentz factors, from 0 min = 2104 to 0 max = 6105. © 2021 Georg Thieme Verlag. All rights reserved. ; The MAGIC Collaboration would like to thank the Instituto de Astrofísica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The financial support of the German BMBF, MPG and HGF; the Italian INFN and INAF; the Swiss National Fund SNF; the ERDF under the Spanish Ministerio de Ciencia e Innovación (MICINN) (FPA2017-87859-P, FPA2017-85668-P, FPA2017-82729-C6-5-R, FPA2017-90566-REDC, PID2019-104114RB-C31, PID2019-104114RB-C32, PID2019-105510GB-C31,PID2019-107847RB-C41, PID2019-107847RB-C42, PID2019-107847RB-C44, PID2019-107988GB-C22); the Indian Department of Atomic Energy; the Japanese ICRR, the University of Tokyo, JSPS, and MEXT; the Bulgarian Ministry of Education and Science, National RI Roadmap Project DO1-268/16.12.2019 and the Academy of Finland grant nr. 320045 is gratefully acknowledged. This work was also supported by the Spanish Centro de Excelencia "Severo Ochoa" SEV-2016-0588, SEV-2017-0709 and CEX2019-000920-S, and "María de Maeztu" CEX2019-000918-M, the Unidad de Excelencia "María de Maeztu" MDM-2015-0509-18-2 and the "la Caixa" Foundation (fellowship LCF/BQ/PI18/11630012) and by the CERCA program of the Generalitat de Catalunya; by the Croatian Science Foundation (HrZZ) Project IP-2016-06-9782 and the University of Rijeka Project 13.12.1.3.02; by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3; the Polish National Research Centre grant UMO-2016/22/M/ST9/00382; and by the Brazilian MCTIC, CNPq and FAPERJ. The important contributions from ETH Zurich grants ETH-10.08-2 and ETH-27.12-1 as well as the funding by the Swiss SNF and the German BMBF (Verbundforschung Astro- und Astroteilchenphysik) and HAP (Helmoltz Alliance for Astroparticle Physics) are gratefully acknowledged. Part of this work is supported by Deutsche Forschungsgemeinschaft (DFG) within the Collaborative Research Center SFB 876 "Providing Information by Resource-Constrained Analysis", project C3. We are thankful for the very valuable contributions from E. Lorenz, D. Renker and G. Viertel during the early phase of the project. We thank the Instituto de Astrofísica de Canarias for allowing us to operate the telescope at the Observatorio del Roque de los Muchachos in La Palma, the Max-Planck-Institut für Physik for providing us with the mount of the former HEGRA CT3 telescope, and the MAGIC collaboration for their support. The Fermi LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States, the Commissariat à l'Energie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucléaire et de Physique des Particules in France, the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK) and Japan Aerospace Exploration Agency (JAXA) in Japan, and the K. A. Wallenberg Foundation, the Swedish Research Council and the Swedish National Space Board in Sweden. Additional support for science analysis during the operations phase is gratefully acknowledged from the Istituto Nazionale di Astrofisica in Italy and the Centre National d'Études Spatiales in France. This work performed in part under DOE Contract DE-AC02-76SF00515. This work made use of data from the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by the National Aeronautics and Space Administration. We thank the NuSTAR Operations, Software, and Calibration teams for support with the execution and analysis of these observations. This research has made use of the NuSTAR Data Analysis Software (NuSTARDAS) jointly developed by the ASI Science Data Center (ASDC; Italy) and the California Institute of Technology (USA). This research has also made use of the XRT Data Analysis Software (XRTDAS) developed under the responsibility of the ASI Science Data Center (ASDC), Italy. A.A.E and D.P acknowledge support from the Deutsche Forschungs gemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy – EXC-2094 – 390783311. M. B. acknowledges support from the YCAA Prize Postdoctoral Fellowship and from the Black Hole Initiative at Harvard University, which is funded in part by the Gordon and Betty Moore Foundation (grant GBMF8273) and in part by the John Templeton Foundation. This publication makes use of data obtained at the Metsähovi Radio Observatory, operated by Aalto University in Finland. This research has made use of data from the OVRO 40-m monitoring program (Richards et al. 2011) which is supported in part by NASA grants NNX08AW31G, NNX11A043G, and NNX14AQ89G and NSF grants AST-0808050 and AST-1109911. I.A. acknowledges financial support from the Spanish "Ministerio de Ciencia e Innovación" (MCINN) through the "Center of Excellence Severo Ochoa" award for the Instituto de Astrofísica de Andalucía-CSIC (SEV-2017-0709). Acquisition and reduction of the MAPCAT data was supported in part by MICINN through grants AYA2016-80889-P and PID2019-107847RB-C44. The MAPCAT observations were carried out at the German-Spanish Calar Alto Observatory, which is jointly operated by Junta de Andalucía and Consejo Superior de Investigaciones Científicas. C.C. acknowledges support from the European Research Council (ERC) under the European Union Horizon 2020 research and innovation program under the grant agreement No 771282. This research was partially supported by the Bulgarian National Science Fund of the Ministry of Education and Science under grants KP-06-H28/3 (2018), KP-06-H38/4 (2019) and KP-06-KITAJ/2 (2020). We acknowledge support by Bulgarian National Science Fund under grant DN18-10/2017 and National RI Roadmap Projects DO1-277/16.12.2019 and DO1-268/16.12.2019 of the Ministry of Education and Science of the Republic of Bulgaria. This research was supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia (contract No 451-03-68/2020-14/200002). G.D. acknowledges observing grant support from the Institute of Astronomy and Rozhen NAO BAS through the bilateral joint research project "Gaia Celestial Reference Frame (CRF) and fast variable astronomical objects" (2020–2022, head – G. Damljanovic). The BU group was supported in part by NASA Fermi guest investigator program grants 80NSSC19K1505 and 80NSSC20K1566. This study was based in part on observations conducted using the 1.8 m Perkins Telescope Observatory (PTO) in Arizona, which is owned and operated by Boston University. This article is partly based on observations made with the LCOGT Telescopes, one of whose nodes is located at the Observatorios de Canarias del IAC on the island of Tenerife in the Observatorio del Teide. This article is also based partly on data obtained with the STELLA robotic telescopes in Tenerife, an AIP facility jointly operated by AIP and IAC. The Abastumani team acknowledges financial support by the Shota Rustaveli National Science Foundation under contract FR-19-6174. Based on observations with the Medicina telescope operated by INAF – Istituto di Radioastronomia. ; Peer reviewed

Kiehlmann, S. et. al. ; Context. Over the past few years, on several occasions, large, continuous rotations of the electric vector position angle (EVPA) of linearly polarized optical emission from blazars have been reported. These events are often coincident with high energy gamma-ray flares and they have attracted considerable attention, since they could allow us to probe the magnetic field structure in the gamma-ray emitting region of the jet. The flat-spectrum radio quasar 3C 279 is one of the most prominent examples showing this behaviour. Aims. Our goal is to study the observed EVPA rotations and to distinguish between a stochastic and a deterministic origin of the polarization variability. Methods. We have combined multiple data sets of R-band photometry and optical polarimetry measurements of 3C 279, yielding exceptionally well-sampled flux density and polarization curves that cover a period of 2008-2012. Several large EVPA rotations are identified in the data. We introduce a quantitative measure for the EVPA curve smoothness, which is then used to test a set of simple random walk polarization variability models against the data. Results. 3C 279 shows different polarization variation characteristics during an optical low-flux state and a flaring state. The polarization variation during the flaring state, especially the smooth similar to 360 degrees rotation of the EVPA in mid-2011, is not consistent with the tested stochastic processes. Conclusions. We conclude that, during the two different optical flux states, two different processes govern polarization variation, which is possibly a stochastic process during the low-brightness state and a deterministic process during the flaring activity. ; S.K. was supported for this research through a stipend from the International Max Planck Research School (IMPRS) for Astronomy and Astrophysics at the Max Planck Institute for Radio Astronomy in cooperation with the Universities of Bonn and Cologne. T.S. was partly supported by the Academy of Finland project 274477. The research at Boston University was partly funded by NASA Fermi GI grant NNX11AQ03G. K.V.S. is partly supported by the Russian Foundation for Basic Research grants 13-02-12103 and 14-02-31789. N.G.B. was supported by the RFBR grant 12-02-01237a. E.B., M.S. and D.H. thank financial support from UNAM DGAPA-PAPIIT through grant IN116211-3. I. A. acknowledges support by a Ramon y Cajal grant of the Spanish Ministry of Economy and Competitiveness (MINECO). The research at the IAA-CSIC and the MAPCAT program are supported by the Spanish Ministry of Economy and Competitiveness and the Regional Government of Andalucia (Spain) through grants AYA2010-14844, AYA2013-40825-P, and P09-FQM-4784. The Calar Alto Observatory is jointly operated by the Max-Planck-Institut fur Astronomie and the Instituto de Astrofisica de Andalucia-CSIC. Data from the Steward Observatory spectropolarimetric monitoring project were used. This program is supported by Fermi Guest Investigator grants NNX08AW56G, NNX09AU10G, NNX12AO93G, and NNX14AQ58G. St. Petersburg University team acknowledges support from Russian RFBR grant 15-02-00949 and St. Petersburg University research grant 6.38.335.2015. The Abastumani team acknowledges financial support of the project FR/638/6-320/12 by the Shota Rustaveli National Science Foundation under contract 31/77. ; Peer reviewed

27 pages, 18 figures, 1 table, 1 appendix.-- Pre-print archive. ; We present numerical simulations of the spectral evolution and emission of radio components in relativistic jets. We have developed an algorithm (SPEV) for the transport of a population of non-thermal electrons including radiative losses. For large values of the ratio of gas pressure to magnetic field energy density, \ab \sim 6\times 10^4, quiescent jet models show substantial spectral evolution, with observational consequences only above radio frequencies. Larger values of the magnetic field (\ab \sim 6\times 10^2), such that synchrotron losses are moderately important at radio frequencies, present a larger ratio of shocked-to-unshocked regions brightness than the models without radiative losses, despite the fact that they correspond to the same underlying hydrodynamic structure. We also show that jets with a positive photon spectral index result if the lower limit \gamma_min of the non-thermal particle energy distribution is large enough. A temporary increase of the Lorentz factor at the jet inlet produces a traveling perturbation that appears in the synthetic maps as a superluminal component. We show that trailing components can be originated not only in pressure matched jets, but also in over-pressured ones, where the existence of recollimation shocks does not allow for a direct identification of such features as Kelvin-Helmholtz modes, and its observational imprint depends on the observing frequency. If the magnetic field is large (\ab \sim 6\times 10^2), the spectral index in the rarefaction trailing the traveling perturbation does not change much with respect to the same model without any hydrodynamic perturbation. If the synchrotron losses are considered the spectral index displays a smaller value than in the corresponding region of the quiescent jet model. ; P. M. has performed this work with a European Union Marie Curie Incoming International Fellowship (MEIFCT- 2005-021603) and with the partial support obtained through the grant CSD-2007-00050. M. A. A. is a Ramón y Cajal Fellow of the Spanish Ministry of Education and Science. We acknowledge the support by the Spanish Ministerio de Educación y Ciencia and the European Fund for Regional Development through grants AYA2007-67626-C03-01, AYA2007-67626-C03-02 and AYA2007-67627-C03-03. I. A. has been supported an I3P contract with the Spanish Consejo Superior de Investigaciones Científicas. ; Peer reviewed

Context. Flares in radio-loud active galactic nuclei are thought to be associated with the injection of fresh plasma into the compact jet base. Such flares are usually strongest and appear earlier at shorter radio wavelengths. Hence, very long baseline interferometry (VLBI) at millimeter(mm)-wavelengths is the best-suited technique for studying the earliest structural changes of compact jets associated with emission flares. Aims. We study the morphological changes of the parsec-scale jet in the nearby (z = 0.049) γ-ray bright radio galaxy 3C 111 following a flare that developed into a major radio outburst in 2007. Methods. We analyse three successive observations of 3C 111 at 86 GHz with the Global mm-VLBI Array (GMVA) between 2007 and 2008 which yield a very high angular resolution of ∼45 μas. In addition, we make use of single-dish radio flux density measurements from the F-GAMMA and POLAMI programmes, archival single-dish and VLBI data. Results. We resolve the flare into multiple plasma components with a distinct morphology resembling a bend in an otherwise remarkably straight jet. The flare-associated features move with apparent velocities of ∼4.0c to ∼4.5c and can be traced also at lower frequencies in later epochs. Near the base of the jet, we find two bright features with high brightness temperatures up to ∼1011 K, which we associate with the core and a stationary feature in the jet. Conclusions. The flare led to multiple new jet components indicative of a dynamic modulation during the ejection. We interpret the bend-like feature as a direct result of the outburst which makes it possible to trace the transverse structure of the jet. In this scenario, the components follow different paths in the jet stream consistent with expectations for a spine-sheath structure, which is not seen during intermediate levels of activity. The possibility of coordinated multiwavelength observations during a future bright radio flare in 3C 111 makes this source an excellent target for probing the radio-γ-ray connection. © ESO 2020. ; We would like to thank the anonymous referee for helpful comments that improved the manuscript. We would like to thank the internal MPIfR referee N. MacDonald for insightful comments that helped improve the manuscript. RS gratefully acknowledge support from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC Advanced Grant RADIOLIFE-320745 and support by Deutsche Forschungsgemeinschaft grant WI 1860/10-1. MP acknowledges financial support from the Spanish Ministry of Science through Grants PID2019-105510GB-C31, PID2019-107427GB-C33 and AYA2016-77237-C3-3-P, and from the Generalitat Valenciana through grant PROMETEU/2019/071. I.A. acknowledges support by a Ramon y Cajal grant (RYC-2013-14511) of the "Ministerio de Ciencia e Innovacion (MICINN)" of Spain. He also acknowledges financial support from MCINN through the "Center of Excellence Severo Ochoa" award for the Instituto de Astrofisica de Andalucia-CSIC (SEV-2017-0709). Acquisition and reduction of the POLAMI data was supported in part by MICINN through grant AYA2016-80889-P. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain). This research has made use of data obtained with the Global Millimeter VLBI Array (GMVA), which consists of telescopes operated by the MPIfR, IRAM, Onsala, Metsahovi, Yebes, the Korean VLBI Network, the Green Bank Observatory and the Very Long Baseline Array (VLBA). The VLBA is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. The data were correlated at the correlator of the MPIfR in Bonn, Germany. This study makes use of 43 GHz VLBA data from the Boston University gamma-ray blazar monitoring program (http://www.bu.edu/blazars/VLBAproject.html), funded by NASA through the Fermi Guest Investigator Program. This research has made use of data from the MOJAVE database that is maintained by the MOJAVE team (Lister et al. 2009). The Very Long Baseline Array (VLBA) is an instrument of the National Radio Astronomy Observatory (NRAO). NRAO is a facility of the National Science Foundation, operated by Associated Universities Inc. This research made use of the Interactive Spectral Interpretation System (ISIS) (Houck & Denicola 2000) and a collection of ISIS scripts provided by the Dr. Karl Remeis observatory, Bamberg, Germany at http://www.sternwarte.uni-erlangen.de/isis/. This research made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration and of the VizieR catalogue access tool, CDS, Strasbourg, France. ; Peer reviewed

Full list of authors: Acharyya, A.; Adam, R.; Adams, C.; Agudo, I.; Aguirre-Santaella, A.; Alfaro, R.; Alfaro, J.; Alispach, C.; Aloisio, R.; Alves Batista, R.; Amati, L.; Ambrosi, G.; Angüner, E. O.; Antonelli, L. A.; Aramo, C.; Araudo, A.; Armstrong, T.; Arqueros, F.; Asano, K.; Ascasíbar, Y. Ashley, M.; Balazs, C.; Ballester, O.; Baquero Larriva, A.; Barbosa Martins, V.; Barkov, M.; Barres de Almeida, U.; Barrio, J. A.; Bastieri, D.; Becerra, J.; Beck, G.; Becker Tjus, J.; Benbow, W.; Benito, M.; Berge, D.; Bernardini, E.; Bernlöhr, K.; Berti, A.; Bertucci, B.; Beshley, V.; Biasuzzi, B.; Biland, A.; Bissaldi, E.; Biteau, J.; Blanch, O.; Blazek, J.; Bocchino, F.; Boisson, C.; Bonneau Arbeletche, L.; Bordas, P.; Bosnjak, Z.; Bottacini, E.; Bozhilov, V.; Bregeon, J.; Brill, A.; Bringmann, T.; Brown, A. M.; Brun, P.; Brun, F.; Bruno, P.; Bulgarelli, A.; Burton, M.; Burtovoi, A.; Buscemi, M.; Cameron, R.; Capasso, M.; Caproni, A.; Capuzzo-Dolcetta, R.; Caraveo, P.; Carosi, R.; Carosi, A.; Casanova, S.; Cascone, E.; Cassol, F.; Catalani, F.; Cauz, D.; Cerruti, M.; Chadwick, P.; Chaty, S.; Chen, A.; Chernyakova, M.; Chiaro, G.; Chiavassa, A.; Chikawa, M.; Chudoba, J.; Çolak, M.; Conforti, V.; Coniglione, R.; Conte, F.; Contreras, J. L.; Coronado-Blazquez, J.; Costa, A.; Costantini, H.; Cotter, G.; Cristofari, P.; D'Aimath, A.; D'Ammando, F.; Damone, L. A.; Daniel, M. K.; Dazzi, F.; De Angelis, A.; De Caprio, V.; de Cássia dos Anjos, R.; de Gouveia Dal Pino, E. M.; De Lotto, B.; De Martino, D.; de Oña Wilhelmi, E.; De Palma, F.; de Souza, V.; Delgado, C.; Delgado Giler, A. G.; della Volpe, D.; Depaoli, D.; Di Girolamo, T.; Di Pierro, F.; Di Venere, L.; Diebold, S.; Dmytriiev, A.; Domínguez, A.; Donini, A.; Doro, M.; Ebr, J.; Eckner, C.; Edwards, T. D. P.; Ekoume, T. R. N.; Elsässer, D.; Evoli, C.; Falceta-Goncalves, D.; Fedorova, E.; Fegan, S.; Feng, Q.; Ferrand, G.; Ferrara, G.; Fiandrini, E.; Fiasson, A.; Filipovic, M.; Fioretti, V.; Fiori, M.; Foffano, L.; Fontaine, G.; Fornieri, O.; Franco, F. J.; Fukami, S.; Fukui, Y.; Gaggero, D.; Galaz, G.; Gammaldi, V.; Garcia, E.; Garczarczyk, M.; Gascon, D.; Gent, A.; Ghalumyan, A.; Gianotti, F.; Giarrusso, M.; Giavitto, G.; Giglietto, N.; Giordano, F.; Giuliani, A.; Glicenstein, J.; Gnatyk, R.; Goldoni, P.; González, M. M.; Gourgouliatos, K.; Granot, J.; Grasso, D.; Green, J.; Grillo, A.; Gueta, O.; Gunji, S.; Halim, A.; Hassan, T.; Heller, M.; Hernández Cadena, S.; Hiroshima, N.; Hnatyk, B.; Hofmann, W.; Holder, J.; Horan, D.; Hörandel, J.; Horvath, P.; Hovatta, T.; Hrabovsky, M.; Hrupec, D.; Hughes, G.; Humensky, T. B.; Hütten, M.; Iarlori, M.; Inada, T.; Inoue, S.; Iocco, F.; Iori, M.; Jamrozy, M.; Janecek, P.; Jin, W.; Jouvin, L.; Jurysek, J.; Karukes, E.; Katarzyński, K.; Kazanas, D.; Kerszberg, D.; Kherlakian, M. C.; Kissmann, R.; Knödlseder, J.; Kobayashi, Y.; Kohri, K.; Komin, N.; Kubo, H.; Kushida, J.; Lamanna, G.; Lapington, J.; Laporte, P.; Leigui de Oliveira, M. A.; Lenain, J.; Leone, F.; Leto, G.; Lindfors, E.; Lohse, T.; Lombardi, S.; Longo, F.; Lopez, A.; López, M.; López-Coto, R.; Loporchio, S.; Luque-Escamilla, P. L.; Mach, E.; Maggio, C.; Maier, G.; Mallamaci, M.; Malta Nunes de Almeida, R.; Mandat, D.; Manganaro, M.; Mangano, S.; Manicò, G.; Marculewicz, M.; Mariotti, M.; Markoff, S.; Marquez, P.; Martí, J.; Martinez, O.; Martínez, M.; Martínez, G.; Martínez-Huerta, H.; Maurin, G.; Mazin, D.; Mbarubucyeye, J. D.; Medina Miranda, D.; Meyer, M.; Miceli, M.; Miener, T.; Minev, M.; Miranda, J. M.; Mirzoyan, R.; Mizuno, T.; Mode, B.; Moderski, R.; Mohrmann, L.; Molina, E.; Montaruli, T.; Moralejo, A.; Morcuende-Parrilla, D.; Morselli, A.; Mukherjee, R.; Mundell, C.; Nagai, A.; Nakamori, T.; Nemmen, R.; Niemiec, J.; Nieto, D.; Nikołajuk, M.; Ninci, D.; Noda, K.; Nosek, D.; Nozaki, S.; Ohira, Y.; Ohishi, M.; Ohtani, Y.; Oka, T.; Okumura, A.; Ong, R. A.; Orienti, M.; Orito, R.; Orlandini, M.; Orlando, S.; Orlando, E.; Ostrowski, M.; Oya, I.; Pagano, I.; Pagliaro, A.; Palatiello, M.; Pantaleo, F. R.; Paredes, J. M.; Pareschi, G.; Parmiggiani, N.; Patricelli, B.; Pavletić, L.; Pe'er, A.; Pecimotika, M.; Pérez-Romero, J.; Persic, M.; Petruk, O.; Pfrang, K.; Piano, G.; Piatteli, P.; Pietropaolo, E.; Pillera, R.; Pilszyk, B.; Pintore, F.; Pohl, M.; Poireau, V.; Prado, R. R.; Prandini, E.; Prast, J.; Principe, G.; Prokoph, H.; Prouza, M.; Przybilski, H.; Pühlhofer, G.; Pumo, M. L.; Queiroz, F.; Quirrenbach, A.; Rainò, S.; Rando, R.; Razzaque, S.; Recchia, S.; Reimer, O.; Reisenegger, A.; Renier, Y.; Rhode, W.; Ribeiro, D.; Ribó, M.; Richtler, T.; Rico, J.; Rieger, F.; Rinchiuso, L.; Rizi, V.; Rodriguez, J.; Rodriguez Fernandez, G.; Rodriguez Ramirez, J. C.; Rojas, G.; Romano, P.; Romeo, G.; Rosado, J.; Rowell, G.; Rudak, B.; Russo, F.; Sadeh, I.; Sæther Hatlen, E.; Safi-Harb, S.; Salesa Greus, F.; Salina, G.; Sanchez, D.; Sánchez-Conde, M.; Sangiorgi, P.; Sano, H.; Santander, M.; Santos, E. M.; Santos-Lima, R.; Sanuy, A.; Sarkar, S.; Saturni, F. G.; Sawangwit, U.; Schussler, F.; Schwanke, U.; Sciacca, E.; Scuderi, S.; Seglar-Arroyo, M.; Sergijenko, O.; Servillat, M.; Seweryn, K.; Shalchi, A.; Sharma, P.; Shellard, R. C.; Siejkowski, H.; Silk, J.; Siqueira, C.; Sliusar, V.; Słowikowska, A.; Sokolenko, A.; Sol, H.; Spencer, S.; Stamerra, A.; Stanič, S.; Starling, R.; Stolarczyk, T.; Straumann, U.; Strišković, J.; Suda, Y.; Suomijarvi, T.; Świerk, P.; Tavecchio, F.; Taylor, L.; Tejedor, L. A.; Teshima, M.; Testa, V.; Tibaldo, L.; Todero Peixoto, C. J.; Tokanai, F.; Tonev, D.; Tosti, G.; Tosti, L.; Tothill, N.; Truzzi, S.; Travnicek, P.; Vagelli, V.; Vallage, B.; Vallania, P.; van Eldik, C.; Vandenbroucke, J.; Varner, G. S.; Vassiliev, V.; Vázquez Acosta, M.; Vecchi, M.; Ventura, S.; Vercellone, S.; Vergani, S.; Verna, G.; Viana, A.; Vigorito, C. F.; Vink, J.; Vitale, V.; Vorobiov, S.; Vovk, I.; Vuillaume, T.; Wagner, S. J.; Walter, R.; Watson, J.; Weniger, C.; White, R.; White, M.; Wiemann, R.; Wierzcholska, A.; Will, M.; Williams, D. A.; Wischnewski, R.; Yanagita, S.; Yang, L.; Yoshikoshi, T.; Zacharias, M.; Zaharijas, G.; Zakaria, A. A.; Zampieri, L.; Zanin, R.; Zaric, D.; Zavrtanik, M.; Zavrtanik, D.; Zdziarski, A. A.; Zech, A.; Zechlin, H.; Zhdanov, V. I.; Živec, M.--Published by IOP Publishing Ltd on behalf of Sissa Medialab. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. ; We provide an updated assessment of the power of the Cherenkov Telescope Array (CTA) to search for thermally produced dark matter at the TeV scale, via the associated gamma-ray signal from pair-annihilating dark matter particles in the region around the Galactic centre. We find that CTA will open a new window of discovery potential, significantly extending the range of robustly testable models given a standard cuspy profile of the dark matter density distribution. Importantly, even for a cored profile, the projected sensitivity of CTA will be sufficient to probe various well-motivated models of thermally produced dark matter at the TeV scale. This is due to CTA's unprecedented sensitivity, angular and energy resolutions, and the planned observational strategy. The survey of the inner Galaxy will cover a much larger region than corresponding previous observational campaigns with imaging atmospheric Cherenkov telescopes. CTA will map with unprecedented precision the large-scale diffuse emission in high-energy gamma rays, constituting a background for dark matter searches for which we adopt state-of-the-art models based on current data. Throughout our analysis, we use up-to-date event reconstruction Monte Carlo tools developed by the CTA consortium, and pay special attention to quantifying the level of instrumental systematic uncertainties, as well as background template systematic errors, required to probe thermally produced dark matter at these energies. © 2021 The Author(s). ; We gratefully acknowledge financial support from the following agencies and organisations: State Committee of Science of Armenia, Armenia; The Australian Research Council, Astronomy Australia Ltd, The University of Adelaide, Australian National University, Monash University, The University of New South Wales, The University of Sydney, Western Sydney University, Australia; Federal Ministry of Education, Science and Research, and Innsbruck University, Austria; Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq), Fundacao de Amparo a Pesquisa do Estado do Rio de Janeiro (FAPERJ), Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP), Ministry of Science, Technology, Innovations and Communications (MCTIC), and Instituto Serrapilheira, Brasil; Ministry of Education and Science, National RI Roadmap Project DO1-153/28.08.2018, Bulgaria; The Natural Sciences and Engineering Research Council of Canada and the Canadian Space Agency, Canada; CONICYT-Chile grants CATA AFB 170002, ANID PIA/APOYO AFB 180002, ACT 1406, FONDECYT-Chile grants, 1161463, 1170171, 1190886, 1171421, 1170345, 1201582, Gemini-ANID 32180007, Chile; Croatian Science Foundation, Rudjer Boskovic Institute, University of Osijek, University of Rijeka, University of Split, Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, University of Zagreb, Faculty of Electrical Engineering and Computing, Croatia; Ministry of Education, Youth and Sports, MEYS LM2015046, LM2018105, LTT17006, EU/MEYS CZ.02.1.01/0.0/0.0/16_013/0001403, CZ.02.1.01/0.0/0.0/18_046/0016007 and CZ.02.1.01/0.0/0.0/16_019/0000754, Czech Republic; Academy of Finland (grant nr.317636, 320045, 317383 and 320085), Finland; Ministry of Higher Education and Research, CNRS-INSU and CNRS-IN2P3, CEA-Irfu, ANR, Regional Council Ile de France, Labex ENIGMASS, OSUG2020, P2IO and OCEVU, France; Max Planck Society, BMBF, DESY, Helmholtz Association, Germany; Department of Atomic Energy, Department of Science and Technology, India; Istituto Nazionale di Astrofisica (INAF), Istituto Nazionale di Fisica Nucleare (INFN), MIUR, Istituto Nazionale di Astrofisica (INAF-OABRERA) Grant Fondazione Cariplo/Regione Lombardia ID 2014-1980/RST_ERC, Italy; ICRR, University of Tokyo, JSPS, MEXT, Japan; Netherlands Research School for Astronomy (NOVA), Netherlands Organization for Scientific Research (NWO), Netherlands; University of Oslo, Norway; Ministry of Science and Higher Education, DIR/WK/2017/12, the National Centre for Research and Development and the National Science Centre, UMO-2016/22/M/ST9/00583, Poland; Slovenian Research Agency, grants P1-0031, P1-0385, I0-0033, J1-9146, J1-1700, N1-0111, and the Young Researcher program, Slovenia; South African Department of Science and Technology and National Research Foundation through the South African Gamma-Ray Astronomy Programme, South Africa; The Spanish Ministry of Science and Innovation and the Spanish Research State Agency (AEI) through grants AYA2016-79724-C4-1-P, AYA2016-80889-P, AYA2016-76012-C3-1-P, BES-2016-076342, ESP2017-87055-C2-1-P, FPA2017-82729-C6-1-R, FPA2017-82729-C6-2-R, FPA2017-82729-C6-3-R, FPA2017-82729-C6-4-R, FPA2017-82729-C6-5-R, FPA2017-82729-C6-6-R, PGC2018-095161-B-I00, PGC2018-095512-B-I00; the \Centro de Excelencia Severo Ochoa"program through grants no. SEV-2015-0548, SEV-2016-0597, SEV-2016-0588, SEV-2017-0709; the "Unidad de Excelencia Maria de Maeztu" program through grant no. MDM-2015-0509; the "Ramon y Cajal" programme through grants RYC-2013-14511, RyC-2013-14660, RYC-2017-22665; and the MultiDark Consolider Network FPA2017-90566-REDC. Atraccion de Talento contract no. 2016-T1/TIC-1542 granted by the Comunidad de Madrid; the "Postdoctoral Junior Leader Fellowship" programme from La Caixa Banking Foundation, grants no. LCF/BQ/LI18/11630014 and LCF/BQ/PI18/11630012; the "Programa Operativo" FEDER2014-2020, Consejeria de Economia y Conocimiento de la Junta de Andalucia (ref. 1257737), PAIDI 2020 (ref. P18-FR-1580), and Universidad de Jaen; the Spanish AEI EQC2018-005094-P FEDER 2014-2020; the European Union's "Horizon 2020" research and innovation programme under Marie Sklodowska-Curie grant agreement no. 665919; and the ESCAPE project with grant no. GA:824064, Spain; Swedish Research Council, Royal Physiographic Society of Lund, Royal Swedish Academy of Sciences, The Swedish National Infrastructure for Computing (SNIC) at Lunarc (Lund), Sweden; State Secretariat for Education, Research and Innovation (SERI) and Swiss National Science Foundation (SNSF), Switzerland; Durham University, Leverhulme Trust, Liverpool University, University of Leicester, University of Oxford, Royal Society, Science and Technology Facilities Council, U.K.; U.S. National Science Foundation, U.S. Department of Energy, Argonne National Laboratory, Barnard College, University of California, University of Chicago, Columbia University, Georgia Institute of Technology, Institute for Nuclear and Particle Astrophysics (INPAC-MRPI program), Iowa State University, the Smithsonian Institution, Washington University McDonnell Center for the Space Sciences, The University of Wisconsin and the Wisconsin Alumni Research Foundation, U.S.A. The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreements No 262053 and No 317446. This project is receiving funding from the European Union's Horizon 2020 research and innovation programs under agreement No 676134. ; Peer reviewed

Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.-- Open Access funding provided by Max Planck Society. ; Context Detailed studies of relativistic jets in active galactic nuclei (AGN) require high-fidelity imaging at the highest possible resolution. This can be achieved using very long baseline interferometry (VLBI) at radio frequencies, combining worldwide (global) VLBI arrays of radio telescopes with a space-borne antenna on board a satellite. Aims. We present multiwavelength images made of the radio emission in the powerful quasar S5 0836+710, obtained using a global VLBI array and the antenna Spektr-R of the RadioAstron mission of the Russian Space Agency, with the goal of studying the internal structure and physics of the relativistic jet in this object. Methods. The RadioAstron observations at wavelengths of 18 cm, 6 cm, and 1.3 cm are part of the Key Science Program for imaging radio emission in strong AGN. The internal structure of the jet is studied by analyzing transverse intensity profiles and modeling the structural patterns developing in the flow. Results. The RadioAstron images reveal a wealth of structural detail in the jet of S5 0836+710 on angular scales ranging from 0.02 mas to 200 mas. Brightness temperatures in excess of 1013 K are measured in the jet, requiring Doppler factors of 100 for reconciling them with the inverse Compton limit. Several oscillatory patterns are identified in the ridge line of the jet and can be explained in terms of the Kelvin Helmholtz (KH) instability. The oscillatory patterns are interpreted as the surface and body wavelengths of the helical mode of the KH instability. The interpretation provides estimates of the jet Mach number and of the ratio of the jet to the ambient density, which are found to be Mj 12 and 0:33. The ratio of the jet to the ambient density should be conservatively considered an upper limit because its estimate relies on approximations. © L. Vega-García et al. 2020 ; L.V.G. is a member of the International Max Planck Research School (IMPRS) for Astronomy and Astrophysics at the Universities of Bonn and Cologne. The RadioAstron project is led by the Astro Space Center of the Lebedev Physical Institute of the Russian Academy of Sciences and the Lavochkin Scientific and Production Association under a contract with the State Space Corporation ROSCOSMOS, in collaboration with partner organizations in Russia and other countries. This research is based on observations correlated at the Bonn Correlator, jointly operated by the Max Planck Institute for Radio Astronomy (MPIfR), and the Federal Agency for Cartography and Geodesy (BKG). The European VLBI Network is a joint facility of European, Chinese, South African and other radio astronomy institutes funded by their national research councils. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Thanks to Phillip Edwards and Alan Roy for the useful comments about the paper. M.P. has been supported by the Spanish Ministerio de Economia y Competitividad (grants AYA2015-66899-C2-1-P and AYA2016-77237-C3-3-P) and the Generalitat Valenciana (grant PROMETEOII/2014/069). This work was partially supported by the COST Action MP0904 Black Holes in a Violent Universe. G.B. acknowledges financial support under the INTEGRAL ASI-INAF agreement 2013-025-R.1. T.S. was supported by the Academy of Finland projects 274477, 284495, and 312496. I.A. acknowledges support by a Ramon y Cajal grant of the Ministerio de Economia, Industria y Competitividad (MINECO) of Spain. The research at the IAA-CSIC was partly supported by the MINECO through grants AYA2016-80889-P, AYA2013-40825-P, and AYA2010-14844. Y.Y.K. was supported in part by the government of the Russian Federation (agreement 05.Y09.21.0018) and the Alexander von Humboldt Foundation. ; Peer reviewed

Context. Investigating the magnetic field structure in the innermost regions of relativistic jets is fundamental to understanding the crucial physical processes giving rise to jet formation, as well as to their extraordinary radiation output up to γ-ray energies. Aims. We study the magnetic field structure of the quasar CTA 102 with 3 and 7 mm VLBI polarimetric observations, reaching an unprecedented resolution (∼50 μas). We also investigate the variability and physical processes occurring in the source during the observing period, which coincides with a very active state of the source over the entire electromagnetic spectrum. Methods. We perform the Faraday rotation analysis using 3 and 7 mm data and we compare the obtained rotation measure (RM) map with the polarization evolution in 7 mm VLBA images. We study the kinematics and variability at 7 mm and infer the physical parameters associated with variability. From the analysis of γ-ray and X-ray data, we compute a minimum Doppler factor value required to explain the observed high-energy emission. Results. Faraday rotation analysis shows a gradient in RM with a maximum value of ∼6 × 10 4 rad m -2 and intrinsic electric vector position angles (EVPAs) oriented around the centroid of the core, suggesting the presence of large-scale helical magnetic fields. Such a magnetic field structure is also visible in 7 mm images when a new superluminal component is crossing the core region. The 7 mm EVPA orientation is different when the component is exiting the core or crossing a stationary feature at ∼0.1 mas. The interaction between the superluminal component and a recollimation shock at ∼0.1 mas could have triggered the multi-wavelength flares. The variability Doppler factor associated with such an interaction is large enough to explain the high-energy emission and the remarkable optical flare occurred very close in time. © ESO 2019. ; DB acknowledges support from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme under grant agreement No 771282. IA acknowledges support by a Ramon y Cajal grant of the Ministerio de Ciencia, Innovacion y Universidades (MICINU) of Spain. The research at the IAA-CSIC was supported in part by the MICINU through grant AYA2016-80889-P. ; Peer Reviewed

We analyze the linear polarization of the relativistic jet in BL Lacertae object OJ 287 as revealed by multi-epoch Very Long Baseline Array images at 43 GHz and monitoring observations at optical bands. The electric-vector position angle of the optical polarization matches that at 43 GHz at locations that are often in the compact millimeter-wave >core> or, at other epochs, coincident with a bright, quasi-stationary emission feature ∼0.2 mas (∼0.9 pc projected on the sky) downstream from the core. This implies that electrons with high enough energies to emit optical synchrotron and γ-ray inverse Compton radiation are accelerated both in the core and at the downstream feature, the latter of which lies ≥10 pc from the central engine. The polarization vector in the stationary feature is nearly parallel to the jet axis, as expected for a conical standing shock capable of accelerating electrons to GeV energies.© 2018. The American Astronomical Society. All rights reserved. ; The authors thank Dr. Ioannis Myserlis for a critical review of a draft of this manuscript. The authors acknowledge financial support by MEXT/JSPS Grant-in-Aid for Scientific Research on Innovative Areas (No. 25120007). M.S. was supported during this study by a JSPS Postdoctoral Fellowship for Research Abroad. The research at Boston University was supported in part by National Science Foundation grant AST-1615796 and NASA Fermi Guest Investigator Program grants NNX14AQ58G and 80NSSC17K0649. The St. Petersburg University team acknowledges support from Russian Science Foundation grant 17-12-01029. I.A. acknowledges support by a Ramon y Cajal grant of the Ministerio de Economia y Competitividad (MINECO) of Spain. The research at the IAA-CSIC was supported in part by the MINECO through grants AYA2016-80889-P, AYA2013-40825-P, and AYA2010-14844; and by the regional government of Andalucia through grant P09-FQM-4784. Calar Alto Observatory is jointly operated by the Max-Planck-Institut fur Astronomie and the IAA-CSIC. The VLBA is an instrument of the Long Baseline Observatory (LBO). The LBO is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Data from the Steward Observatory spectro-polarimetric monitoring project were used. This program was supported by Fermi Guest Investigator grants NNX08AW56G, NNX09AU10G, NNX12AO93G, and NNX15AU81G.

Context. While studies of large samples of jets of active galactic nuclei (AGN) are important in order to establish a global picture, dedicated single-source studies are an invaluable tool for probing crucial processes within jets on parsec scales. These processes involve in particular the formation and geometry of the jet magnetic field as well as the flow itself. Aims. We aim to better understand the dynamics within relativistic magneto-hydrodynamical flows in the extreme environment and close vicinity of supermassive black holes. Methods. We analyze the peculiar radio galaxy 3C 111, for which long-Term polarimetric observations are available. We make use of the high spatial resolution of the VLBA network and the MOJAVE monitoring program, which provides high data quality also for single sources and allows us to study jet dynamics on parsec scales in full polarization with an evenly sampled time-domain. While electric vectors can probe the underlying magnetic field, other properties of the jet such as the variable (polarized) flux density, feature size, and brightness temperature, can give valuable insights into the flow itself. We complement the VLBA data with data from the IRAM 30-m Telescope as well as the SMA. Results. We observe a complex evolution of the polarized jet. The electric vector position angles (EVPAs) of features traveling down the jet perform a large rotation of &180across a distance of about 20 pc. As opposed to this smooth swing, the EVPAs are strongly variable within the first parsecs of the jet.We find an overall tendency towards transverse EVPAs across the jet with a local anomaly of aligned vectors in between. The polarized flux density increases rapidly at that distance and eventually saturates towards the outermost observable regions. The transverse extent of the flow suddenly decreases simultaneously to a jump in brightness temperature around where we observe the EVPAs to turn into alignment with the jet flow. Also the gradient of the feature size and particle density with distance steepens significantly at that region. Conclusions. We interpret the propagating polarized features as shocks and the observed local anomalies as the interaction of these shocks with a localized recollimation shock of the underlying flow. Together with a sheared magnetic field, this shock-shock interaction can explain the large rotation of the EVPA. The superimposed variability of the EVPAs close to the core is likely related to a clumpy Faraday screen, which also contributes significantly to the observed EVPA rotation in that region.© ESO 2018. ; T.B. is grateful for fruitful discussions with M. Lyutikov and E. Kravchenko, and thanks D. Gabuzda for her input that helped to improve the paper. We thank the National Radio Astronomy Observatory, a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.; this research has made use of data from the MOJAVE database that is maintained by the MOJAVE team (Lister et al. 2009) and IRAM, which is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain). This work has benefited from research funding from the European Community's Seventh Framework Programme. The Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics and is funded by the Smithsonian Institution and the Academia Sinica. We also thank J. E. Davis for the development of the slxfig module that has been used to prepare the figures in this work. We made use of ISIS functions provided by ECAP/Remeis observatory and MIT (http://www.sternwarte.uni-erlangen.de/isis/) as well as the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. M.P. acknowledges financial support from the Spanish Ministerio de Economia, Industria y Competitividad (grants AYA2013-40979-P, and AYA2013-48226- C3-2-P) and from the local Valencian Government (Generalitat Valenciana, grant Prometeo-11/2014/069). I.A. acknowledges support by a Ramon y Cajal grant of the Ministerio de Economia y Competitividad (MINECO) of Spain. A.B.P. and Y.Y.K. acknowledge partial support by the Russian Foundation for Basic Research (grant 17-02-00197), by the government of the Russian Federation (agreement 05.Y09.21.0018), and by the Alexander von Humboldt Foundation. E.R. acknowledges partial support by the Spanish MINECO project AYA2012-38491-C02-01 and by the Generalitat Valenciana project PROMETEOII/2014/057. T.S. was funded by the Academy of Finland projects 274477 and 284495. The research at the IAA-CSIC was supported in part by the MINECO through grants AYA2016-80889-P, AYA2013-40825-P, and AYA2010-14844, and by the regional government of Andalucia through grant P09-FQM-4784.

The binary neutron star merger event GW170817 was detected through both electromagnetic radiation and gravitational waves. Its afterglow emission may have been produced by either a narrow relativistic jet or an isotropic outflow. High-spatial-resolution measurements of the source size and displacement can discriminate between these scenarios. We present very-long-baseline interferometry observations, performed 207.4 days after the merger by using a global network of 32 radio telescopes. The apparent source size is constrained to be smaller than 2.5 milli-arc seconds at the 90% confidence level. This excludes the isotropic outflow scenario, which would have produced a larger apparent size, indicating that GW170817 produced a structured relativistic jet. Our rate calculations show that at least 10% of neutron star mergers produce such a jet.© 2019 The Authors, some rights reserved. All rights reserved. ; The National Institute of Astrophysics is is acknowledged for PRIN-grant (2017) 1.05.01.88.06. The Italian Ministry for University and Research (MIUR) is acknowledged through the project >FIGARO> (Prin-MIUR) grant 1.05.06.13. ASI is acknowledged for grant I/004/11/3. The research leading to these results has received funding from the European Commission Horizon 2020 Research and Innovation Programme under grant agreement 730562 (RadioNet). The Spanish Ministerio de Economa y Competitividad (MINECO) is acknowledged for financial support under grants AYA201676012-C3-1-P, FPA2015-69210-C6-2-R, and MDM-2014-0369 of ICCUB (Unidad de Excelencia >Mara de Maeztu>). M.A.P.-T. acknowledges support from the Spanish MINECO through grants AYA2012-38491-C02-02 and AYA2015-63939-C2-1-P.T.A. is supported by the National Key R&D Programme of China (2018YFA0404603). E.C.-M. acknowledges support from the European Union's Horizon 2020 research and innovation program under grant agreement 653477. S.F. thanks the Hungarian National Research, Development and Innovation Office (OTKA NN110333) for support. The Long Baseline Array is part of the Australia Telescope National Facility, which is funded by the Australian Government for operation as a National Facility managed by CSIRO. ; Peer Reviewed

The object 4C 71.07 is a high-redshift blazar whose spectral energy distribution shows a prominent big blue bump and a strong Compton dominance. We present the results of a 2- yr multiwavelength campaign led by the Whole Earth Blazar Telescope (WEBT) to study both the quasar core and the beamed jet of this source. The WEBT data are complemented by ultraviolet and X-ray data from Swift, and by γ-ray data by Fermi. The big blue bump is modelled by using optical and near-infrared mean spectra obtained during the campaign, together with optical and ultraviolet quasar templates. We give prescriptions to correct the source photometry in the various bands for the thermal contribution, in order to derive the non-thermal jet flux. The role of the intergalactic medium absorption is analysed in both the ultraviolet and X-ray bands.We provide opacity values to deabsorb ultraviolet data, and derive a best-guess value for the hydrogen column density of Nbest H = 6.3 × 10 cmthrough the analysis of X-ray spectra.We estimate the disc and jet bolometric luminosities, accretion rate, and black hole mass. Light curves do not show persistent correlations among flux changes at different frequencies. We study the polarimetric behaviour and find no correlation between polarization degree and flux, even when correcting for the dilution effect of the big blue bump. Similarly, wide rotations of the electric vector polarization angle do not seem to be connected with the source activity.© 2019 The Author(s). ; We acknowledge financial contribution from the agreement ASI-INAF n.2017-14-H.0 and from the contract PRIN-SKA-CTA-INAF 2016. PR and SV acknowledge contract ASI-INAF I/004/11/0. We acknowledge support by Bulgarian National Science Programme 'Young Scientists and Postdoctoral Students 2019', Bulgarian National Science Fund under grant DN18-10/2017 and National RI Roadmap Projects DO1-157/28.08.2018 and DO1-153/28.08.2018 of the Ministry of Education and Science of the Republic of Bulgaria. GD and OV gratefully acknowledge the observing grant support from the Institute of Astronomy and Rozhen National Astronomical Observatory, Bulgarian Academy of Sciences via bilateral joint research project 'Study of ICRF radio-sources and fast variable astronomical objects' (head -G.Damljanovic). This work is a part of the Projects No. 176011 ('Dynamics and Kinematics of Celestial Bodies and Systems'), No. 176004 ('Stellar Physics'), and No. 176021 ('Visible and Invisible Matter in Nearby Galaxies: Theory and Observations') supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia. This research was partially supported by the Bulgarian National Science Fund of theMinistry of Education and Science under grants DN 08-1/2016, DN 18-13/2017, and KP-06-H28/3 (2018). The Skinakas Observatory is a collaborative project of the University of Crete, the Foundation for Research and Technology -Hellas, and the Max-Planck-Institut fur Extraterrestrische Physik. The St Petersburg University team acknowledges support from Russian Science Foundation grant no. 17-12-01029. The Abastumani team acknowledges financial support by the Shota Rustaveli National Science Foundation under contract FR/217950/16. This work was partly supported by the National Science Fund of the Ministry of Education and Science of Bulgaria under grant DN 08-20/2016, and by funds of the project RD-08-37/2019 of the University of Shumen. The Astronomical Observatory of the Autonomous Region of the Aosta Valley (OAVdA) is managed by the Fondazione Clement Fillietroz-ONLUS, which is supported by the Regional Government of the Aosta Valley, the Town Municipality of Nus and the Unite des Communes valdotaines Mont-Emilius'. The research at the OAVdA was partially funded by two 'Research and Education' grants from Fondazione CRT

Context. The flat-spectrum radio quasar 4C +71.07 is a high-redshift (z = 2.172), γ-loud blazar whose optical emission is dominated by thermal radiation from the accretion disc. Aims. 4C +71.07 has been detected in outburst twice by the AGILE γ-ray satellite during the period from the end of October to mid-November 2015, when it reached a γ-ray flux of the order of F(E > 100 MeV)=(1.2 ± 0.3)×10 photons cm s and F(E > 100 MeV)=(3.1 ± 0.6)×10 photons cm s, respectively, allowing us to investigate the properties of the jet and the emission region. Methods. We investigated its spectral energy distribution by means of almost-simultaneous observations covering the cm, mm, near-infrared, optical, ultraviolet, X-ray, and γ-ray energy bands obtained by the GASP-WEBT Consortium and the Swift, AGILE, and Fermi satellites. Results. The spectral energy distribution of the second γ-ray flare (whose energy coverage is more dense) can be modelled by means of a one-zone leptonic model, yielding a total jet power of about 4 × 10 erg s. Conclusions. During the most prominent γ-ray flaring period our model is consistent with a dissipation region within the broad-line region. Moreover, this class of high-redshift, flat-spectrum radio quasars with high-mass black holes might be good targets for future γ-ray satellites such as e-ASTROGAM. © ESO 2019. ; AGILE is an ASI space mission developed with programmatic support by INAF and INFN. We acknowledge partial support through the ASI grant no. I/028/12/0. SV and PR acknowledge contract ASI-INAF I/004/11/0 and INAF/IASF Palermo where most of the work was carried out. SV acknowledges financial contribution from the agreement ASI-INAF no. 2017-14-H.0. Part of this work is based on archival data, software, or online services provided by the ASI SPACE SCIENCE DATA CENTER (ASI-SSDC). SV and PR thank Leonardo Barzaghi and Sara Baitieri for useful discussions. The Osservatorio di Torino team acknowledges the financial contribution from the agreement ASI-INAF No. 2017-14-H.0 and from the contract PRIN-SKA-CTA-INAF 2016. OMK acknowledges financial support from the Shota Rustaveli National Science Foundation under contract FR/217950/16 and grants NSFC11733001, NSFCU1531245. IA acknowledges support from a Ramón y Cajal grant of the Ministerio de Economía y Compet-itividad (MINECO) of Spain. The research at the IAA–CSIC was supported in part by the MINECO through grants AYA2016–80889–P, AYA2013–40825–P, and AYA2010–14844, and by the regional government of Andalucía through grant P09–FQM–4784. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). Calar Alto Observatory is jointly operated by the MPIA and the IAA-CSIC. This research was partially supported by the Bulgarian National Science Fund of the Ministry of Education and Science under grant DN 08-1/2016. The St. Petersburg University team acknowledges support from Russian Science Foundation grant 17-12-01029. AZT-24 observations are made within an agreement among the Pulkovo, Rome, and Teramo observatories. GD and OV gratefully acknowledge the observing grant support from the Institute of Astronomy and Rozhen National Astronomical Observatory, Bulgaria Academy of Sciences, via bilateral joint research project "Observations of ICRF radio-sources visible in optical domain" (PI G. Damljanovic). This work is a part of Project No. 176011 ("Dynamics and kinematics of celestial bodies and systems"), No. 176004 ("Stellar physics") and No. 176021 ("Visible and invisible matter in nearby galaxies: theory and observations") supported by the Ministry of Education, Science, and Technological Development of the Republic of Serbia. The Maidanak Observatory team acknowledges support from Uzbekistan Academy of Sciences grants No. F2-FA-F027 and F.4-16. ; Peer Reviewed

We report on long-term multiwavelength monitoring of blazar Mrk 421 by the GLAST-AGILE Support Program of the Whole Earth Blazar Telescope (GASP-WEBT) collaboration and Steward Observatory, and by the Swift and Fermi satellites. We study the source behaviour in the period 2007-2015, characterized by several extreme flares. The ratio between the optical, X-ray and γ-ray fluxes is very variable. The γ-ray flux variations show a fair correlation with the optical ones starting from 2012. We analyse spectropolarimetric data and find wavelength-dependence of the polarization degree (P), which is compatible with the presence of the host galaxy, and no wavelength dependence of the electric vector polarization angle (EVPA). Optical polarimetry shows a lack of simple correlation between P and flux and wide rotations of the EVPA. We build broad-band spectral energy distributions with simultaneous near-infrared and optical data from the GASP-WEBT and ultraviolet and X-ray data from the Swift satellite. They show strong variability in both flux and X-ray spectral shape and suggest a shift of the synchrotron peak up to a factor of ~50 in frequency. The interpretation of the flux and spectral variability is compatible with jet models including at least two emitting regions that can change their orientation with respect to the line of sight.© 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. ; The Abastumani team acknowledges financial support by Shota Rustaveli NSF under contract FR/577/6-320/13. The research at BU was supported in part by US National Science Foundation grant AST-1615796 and NASA Fermi Guest Investigator grant NNX14AQ58G. This study makes use of 43 GHz VLBA data from the VLBA-BU Blazar Monitoring Program (VLBA-BUBLAZAR; http://www.bu.edu/blazars/VLBAproject.html), funded by NASA through the Fermi Guest Investigator Program. The PRISM camera at the Lowell Observatory was developed by K. Janes et al. at the BU and Lowell Observatory, with funding from the NSF, BU and Lowell Observatory. This research has made use of data from the MOJAVE data base, which is maintained by the MOJAVE team (Lister et al. 2009). The St. Petersburg University team acknowledges support from Russian RFBR grant 15-02-00949 and St. Petersburg University research grant 6.38.335.2015. This paper is partly based on observations carried out at the German Spanish Calar Alto Observatory, which is jointly operated by the MPIA and the IAA-CSIC. IA research is supported by a Ramon y Cajal grant of the Spanish Ministerio de Economia y Competitividad (MINECO). Acquisition of the MAPCAT data was supported in part by MINECO through grants AYA2010-14844, AYA2013-40825-P and AYA2016-80889-P, and by the Regional Government of Andalucia through grant P09-FQM-4784. This research was partially supported by the Scientific Research Fund of the Bulgarian Ministry of Education and Sciences under grants DO 02-137 (BIn-13/09) and DN 08/1. The Skinakas Observatory is a collaborative project of the University of Crete, the Foundation for Research and Technology - Hellas and the Max-Planck-Institut fur Extrater-restrische Physik. GD and OV gratefully acknowledge the observing grant support from the Institute of Astronomy and Rozhen National Astronomical Observatory, Bulgaria Academy of Sciences, via the bilateral joint research project 'Observations of ICRF radio-sources visible in optical domain' (the head is Dr G. Damljanovic). This work is a part of the Projects No 176011 ('Dynamics and kinematics of celestial bodies and systems'), No 176004 ('Stellar physics') and No 176021 ('Visible and invisible matter in nearby galaxies: theory and observations') supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia. The Serbian station is the Astronomical Station Vidojevica (ASV) with the 60-cm ASV telescope (and from this year, the 1.4-m ASV one). This research was supported partly by funds of the project RD-08-81 of the Shumen University. ; Peer Reviewed

The mechanisms producing fast variability of the γ-ray emission in active galactic nuclei (AGNs) are under debate. The MAGIC telescopes detected a fast, very-high-energy (VHE, E > 100 GeV) γ-ray flare from BL Lacertae on 2015 June 15. The flare had a maximum flux of (1.5 ± 0.3) × 10-10 photons cm-2 s-1 and halving time of 26 ± 8 min. The MAGIC observations were triggered by a high state in the optical and high-energy (HE, E > 100 MeV) γ-ray bands. In this paper we present the MAGIC VHE γ-ray data together with multi-wavelength data from radio, optical, X-rays, and HE γ rays from 2015 May 1 to July 31. Well-sampled multi-wavelength data allow us to study the variability in detail and compare it to the other epochs when fast, VHE γ-ray flares have been detected from this source. Interestingly, we find that the behaviour in radio, optical, X-rays, and HE γ-rays is very similar to two other observed VHE γ-ray flares. In particular, also during this flare there was an indication of rotation of the optical polarization angle and of activity at the 43 GHz core. These repeating patterns indicate a connection between the three events. We also test modelling of the spectral energy distribution based on constraints from the light curves and VLBA observations, with two different geometrical setups of two-zone inverse Compton models. In addition we model the γ-ray data with the star-jet interaction model. We find that all of the tested emission models are compatible with the fast VHE γ-ray flare, but all have some tension with the multi-wavelength observations. © ESO 2019. ; The financial support of the German BMBF and MPG, the Italian INFN and INAF, the Swiss National Fund SNF, the ERDF under the Spanish MINECO (FPA2015-69818-P, FPA2012-36668, FPA 2015-68378-P, FPA2015-69210-C6-2-R, FPA2015-69210-C6-4-R, FPA201569210-C6-6-R, AYA2015-71042-P, AYA2016-76012-C3-1-P, ESP2015-71662C2-2-P, FPA201790566REDC), the Indian Department of Atomic Energy and the Japanese JSPS and MEXT is gratefully acknowledged. This work was also supported by the Spanish Centro de Excelencia >Severo Ochoa> SEV-2016-0588 and SEV-2015-0548, and Unidad de Excelencia >Maria de Maeztu> MDM-20140369, by the Croatian Science Foundation (HrZZ) Project IP-2016-06-9782 and the University of Rijeka Project 13.12.1.3.02, by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, the Polish National Research Centre grant UMO-2016/22/M/ST9/00382 and by the Brazilian MCTIC, CNPq and FAPERJ. The work of the author M. Vazquez Acosta is financed with grant RYC-2013-14660 of MINECO. F. D'Ammando is grateful for support from the National Research Council of Science and Technology, Korea (EU16-001). The Fermi-LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States, the Commissariat a l'Energie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucleaire et de Physique des Particules in France, the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK) and Japan Aerospace Exploration Agency (JAXA) in Japan, and the K. A. Wallenberg Foundation, the Swedish Research Council and the Swedish National Space Board in Sweden. Additional support for science analysis during the operations phase is gratefully acknowledged from the Istituto Nazionale di Astrofisica in Italy and the Centre National d'Etudes Spatiales in France. This work performed in part under DOE Contract DE-AC02-76SF00515. Based on observations made with the Nordic Optical Telescope, operated by the Nordic Optical Telescope Scientific Association at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias. ; Acquisition and reduction of the MAPCAT data was supported in part by MINECO through grants AYA201014844, AYA2013-40825-P, and AYA2016-80889-P, and by the Regional Government of Andalucia through grant P09-FQM-4784. The MAPCAT observations were carried out at the German-Spanish Calar Alto Observatory, which is jointly operated by the Max-Plank-Institut fur Astronomie and the Instituto de Astrofisica de Andalucia-CSIC. The St. Petersburg University team acknowledges support from Russian Science Foundation grant 17-12-01029. This publication makes use of data obtained at the Metsahovi Radio Observatory, operated by Aalto University, Finland. This study makes use of 43-GHz VLBA data from the VLBA-BU Blazar Monitoring Program (VLBA-BUBLAZAR; http://www.bu.edu/blazars/VLBAproject.html), funded by NASA through the Fermi Guest Investigator Program. The VLBA is an instrument of the National Radio Astronomy Observatory. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated by Associated Universities, Inc. The BU group acknowledges support from NASA Fermi GI program grant 80NSSC17K0694 and US National Science Foundation grant AST-1615796. The OVRO 40-m monitoring program is supported in part by NASA grants NNX08AW31G, NNX11A043G and NNX14AQ89G, and NSF grants AST-0808050 and AST-1109911. ; Peer Reviewed